I thought the same, but I was told I need to install COTURN Server.
I don’t know what “HPB service down” means or how it’s related to TALK app. It could be related and hopefully someone will respond to that part.
From what others told me and explained in my question about Turn and Coturn servers etc. They indicated I needed Coturn and this indeed makes my TALK app work as expected both phone talk and video etc working perfectly.
I wish someone would respond to the subject of “HPB service down” and if that is somehow also related.
Here is our discussion when I was working on getting mine working too.
https://help.nextcloud.com/t/nextcloud-talk-app-could-not-establish-a-connection-a-turn-server/131069/8
And FYI “does not work with IPv6.”
Hope this helps.